Vehicle fuel systems comprise, among others, a fuel tank fitted with a filler neck, a variety of fuel valves, a tubing for supplying fuel to the ignition system and a fuel vapor treating system (typically a carbon filter recovery system often referred to as a carbon canister) to which fuel vapor from the fuel tank flows and is then used for enriching the fuel mixture fed to the ignition system.
Fuel fluid (in the form of liquid, droplets, spray and vapor) from the fuel tank flows via the one or more valves which are connected, via suitable tubing, to a liquid trap intermediate the fuel vapor recovery system and the tank.
The liquid trap receives fuel fluid flowing from the fuel tank which flow at a relatively high velocity owing to pressure and temperature changes, and thus vapor flowing from the fuel tank carries along with it also a considerable amount of fuel liquid in the form of droplets. The liquid trap entraps the fuel liquid and allows fuel vapor flow towards the vapor recovery system. The fuel liquid then returns back to the fuel tank, upon pressure decrease within the fuel tank.
An important factor in attaching accessories to a fuel tank is maintaining a fuel-impermeability so as to comply with strict environmental regulations. One common practice to connect a valve to a fuel tank is by performing an aperture of a size comfortably accommodating the valve's housing, and fixedly attaching the valve by various means, e.g. welding, heat welding, different fasteners, etc. However, according to these methods, there is a need to provide special sealing means between the valve's housing and the tank.
According to another technique fuel valves are attached to the fuel tank by fusion welding the valve to the inside upper surface of the fuel tank. Alternatively, a coupler element is securely attached to the upper surface of the fuel tank and the valve is fixed to said coupler element.
The external surface of a tank holding one or more valves also carries at least a portion of an outlet nozzle and tubing connected thereto, as well as, in some cases, also some electrical wiring. This requires special space design of the fuel tank, and other considerations.
Another consideration concerned with connection of valves to tanks is the effective operation level of the valves, namely the level at which the valve closes (at times referred to as cut-off or shut-off and the level at which the valve reopens. One of the considerations governing the operative level is space consuming which is of significant importance in particular in vehicles. It is thus a requirement that the “dead space” i.e. the space between “maximum fuel level” and the top wall of the fuel tank, be reduced to minimum. However, by inserting the valve into the tank, care has to be taken not to increase the dead space.
Another parameter of concern is the time required for assembling and attaching each individual fuel vapor accessory to the fuel tank and to the articulated coupling tubing, and the costs involved therewith.
The ever-growing requirement of environment concerned organizations and authorities that the rate of fuel permeability from the fuel tank and its accessories be minimal. The outcome of this requirement is that new connection means are now required for ensuring essentially permeation-free connection between the valves and the fuel tank.
It is thus a growing trend to form as little as possible openings in the tank (ideally only one), and accordingly a venting system with its associated valves and connections are relocated as far as possible into the tank.
It is an object of the present invention to provide a concept for attaching fuel vapor accessories within a fuel tank in a substantially fuel impermeable manner. It is a further object of the invention to provide a fuel-flow coupling system interconnecting the various fuel vapor accessories. These and other objects are carried out in a substantially fuel impermeable manner, which is considered to be substantially fast and cost effective.